1. Field of the Invention
The present invention relates to an orientation layer for liquid crystal elements and methods of producing the same, which is provided to cause an alignment of liquid crystal molecules in a specified direction.
2. Description of the Related Art
Known orientation layers for liquid crystal element include: a layer obtained by subjecting a layer consisting of such insulating materials as a polyimide resin to a rubbing treatment where it is unidirectionally rubbed by means of a cloth or the like; and a layer formed by obliquely depositing silicon dioxide (SiO.sub.2).
The orientation layer treated with a rubbing as described, however, has a problem that dust is caused and/or static electricity is generated when rubbing it by a cloth or the like in order to fabricate the orientation layer. On the other hand, the layer obtained by the oblique-deposition has, in addition to its too large fabrication costs, a problem that it is unable to respond to an increase in the size of the liquid crystal elements, since it is difficult to form the layer as one having a large area.
An orientation layer formed by a transfer method is known as the orientation layer capable of coping with such problems. The orientation layer by such transfer method is a layer on the surface of which ruggedness is formed by means of transfer by pressing a mold in a heated condition onto a resinous layer which has been formed on a substrate. The orientation layer based on such conventional transfer method has been formed as having a large number of projecting stripes repeated substantially in parallel to each other on the substrate.
Since, however, a pretilt angle is not obtained with the orientation layer formed by such conventional transfer method, there is a problem that unevenness occurs within the surface of a display screen whereby disclination tends to occur. This has been a decisive disadvantage for a crystal liquid element. In general, it is known that disclination hardly occurs for the pretilt angle of one degree or more.
Even though a very small amount of pretilt angle may be obtained, its distribution within the screen is uneven due to disorder in the convex condition so that unevenness occurs on the display screen. Further, a liquid crystal element using an orientation layer on which ruggedness is formed simply by means of the transfer method has a relatively weak boundary regulating force, whereby its reliability against an external force and/or heat is inferior.